1. Field of the Invention
The invention relates to de-inking systems and, more particularly, relates to a system and process for removing soluble ink from newsprint or the like using a counterflow extractor.
2. Discussion of the Related Art
Systems for extracting soluble ink from newsprint or the like are well known. Such systems typically employ at least a six-stage batch de-inking process in which individual batches of newsprint pulp are each repeatedly slurried and de-watered through compression until, at the end of the process, substantially all of the ink has been removed from the fibrous paper product. Specifically, the newsprint, after being soaked in a tank and turned into a pulp, is soaked in a relatively large reactor tank, pumped out, and compressed, thereby removing some of the ink. The partially de-inked pulp is then soaked in another tank, pumped out, and recompressed, thereby removing more ink. This process is typically repeated at least 6 times and, depending upon the degree of de-inking required and the quality of the fibers being treated, may require 12 or more de-inking stages before de-inking is complete.
The conventional de-inking system and process exhibits several drawbacks and disadvantages. For instance, the system is relatively complex and requires at least 6 reactor tanks for removing the ink and associated presses and filters for de-watering. Such a complex system requires considerable space and capital expenditure rendering newspaper de-inking uneconomical for many businesses and municipalities.
In addition, the traditional de-inking process employing at least 6--and typically 12 or more--reactor tanks expends large quantities of water which is polluted in the de-inking process and which must be treated for re-use, thus further increasing process cost. Even if the pollution problem could be dealt with adequately, many businesses and municipalities in arid climates cannot afford the water required for de-inking--assuming of course that sufficient water is available. The need has therefore arisen to remove economically ink from newsprint or the like using as little water as possible.